This invention relates to the treatment of cellulosic materials, such as paper, with an organo silicon halide to impart water repellency and other desirable properties to the treated material.
It has long been known that material treated with organo silicon halides may be rendered water repellent, apparently through the formation of a siloxane deposit which is formed by a reaction between the halide and adsorbed surface moisture and/or hydroxyl or other reactive groups. In the treatment, hydrogen halide is generated as a reaction by-product. It is also known that paper, cloth and related materials may be made adhesive, or given "release" or non-sticking properties, by treatment with organo silicone reagents in such a way as to produce a silicon-containing layer on the surface of the material. This treatment may also produce hydrogen halide as a by-product.
In these prior art treatments, the cellulosic material has been contacted with the organo silicon halide either in liquid or vapor form. However, the conditions under which these prior art treatments have been conducted require that the treated cellulosic material be further treated to neutralize the hydrogen halide by-product formed by the reaction of the organo silicon halide with water or hydroxyl groups. Heretofore, the treatment of cellulosic materials to obtain these and other possible benefits has required that the treated material be neutralized immediately after exposure to the organo silicon halide by immersion in an aqueous alkaline medium. Consequently it has not been practical to treat material such a as paper with an organo silicon halide because of its unsuitability to a subsequent neutralization step in an aqueous medium. The suggestion has been made to neutralize the hydrogen halide by means of an ammonia atmosphere, but this results only in the formation of ammonium chloride which is itself acidic and causes degradation of the cellulose. Other processes for waterproofing paper are of course available, but none offers the ease and economy of a simple treatment of exposing the paper to a treating atmosphere. Accordingly, it would be highly desirable to provide a process for rendering cellulosic materials, particularly paper, water repellent with an organo silicon halide while retaining the strength characteristics of the paper and while eliminating the need for a subsequent treating step whereby the hydrogen halide is neutralized.